Wind farm and method for installing a wind farm

ABSTRACT

It comprises a number of wind turbines having a modular jacket formed of at least an upper substructure, an intermediate substructure, and a lower substructure that are connectable to each other. At least the intermediate substructure in a wind turbine foundation is different in height (h) from at least one substructure in another wind turbine foundation in order to adapt the different wind turbines of the wind farm to a site having differences in depth (ΔH) where the wind turbines of the wind farm are installed of the order of about 20 to 60 m.

TECHNICAL FIELD

A wind farm and method for installing such a wind farm.

As used herein, a wind farm is a group of at least two wind turbinesthat are installed in the same location for producing electric power.Locations, such as offshore or onshore are herein envisaged for thepresent wind farm.

The present disclosure is particularly focused to foundation structuresof wind turbines in a wind farm comprising jackets.

BACKGROUND

Jacket foundations are known in wind turbine foundations. They comprisea structure intended to support the wind turbine, and particularly thewind turbine tower. Jacket foundations typically comprise a steel framein the form of a lattice tower including a number of connecting members.The connecting members are connected to each other by means of bracingsand tubular joints.

In offshore applications, for example, the jacket foundations are fittedin conjunction with a number of piles into the sea bed for appropriatelytransferring structural loads from the tower to the sea bed. The pilesare steel elongated pieces intended to be driven into the sea bed. Pilesare shaped for receiving corresponding pins. The pins are elongatedconnecting members extending downwards from the wind turbine foundation.

When the pins are inserted into the corresponding piles a highperformance concrete-like mass such as grout is injected. The grout isinjected typically through the bottom of a chamber formed between thepile and the pin thus forming a grouted joint. Grout injection servesthe purpose of establishing a firm connection between the piles and thepins. Grout injection also helps to avoid undesirable horizontaldeflections and inhibit corrosion. The grout provides an increasedenergy absorption capacity to the structure of the foundation.

Jacket foundations formed of a number of substructures are known in theart. They are used in applications such as in the oil and gas sector.Jacket foundations comprising substructures in the field of wind energyare totally dynamically different from oil and gas structures, and theyare starting their development.

At present, wind turbine foundations are constructed with varyingstructural features in order to adapt to different sites havingdifferent characteristics, such as sea depth. In order to obtain thehighest level of standardization of the wind turbine foundations whileadapting to most sites, the distance between the piles in the jacket maybe made constant. This however has the disadvantage that the inclinationof the connecting members of the jacket needs to be varied. This has thedisadvantage that the joints in the vertical and diagonal bar members ofthe jacket structure are changed. A known alternative solution iskeeping the inclination of the connecting members of the jacketconstant. This however has the disadvantage that the foot unit or baseis changed so that a different specific foot unit or base is required tobe made for each position in the site in order to properly fit thepiles.

In document U.S. Pat. No. 5,356,239 a modular jacket assembly isdisclosed comprising interchangeable stackable substructures. Thesubstructures comprise vertical members, some of which are adapted toallow the passage of piles. The technical problem this document dealswith is the manufacture of parts having different sizes to be adapted todifferent sites having different features.

Document WO2012052029 discloses wind turbine foundations comprisingstackable substructures arranged on a base placed on the sea bed and aplurality of tensioning elements extending from the base to a locationadjacent the surface of the water. As above, this solution is focused onthe manufacturing of different foundations to be adapted to differentsites having different features.

The above arrangements do not deal with the same wind farm site havingdifferent features. There are many locations where a wind farm isinstalled having large differences in sea depth, for example in the caseof offshore applications. In the prior art, this involves the use ofquite different jacket structures for wind turbines installed in thesame wind farm site where varying features such as sea depth, inoffshore applications, are present. This directly affects the design ofmost of the wind turbine components, resulting in complex and costlymanufacturing, transportation and installation processes. This isparticularly relevant since in recent years, larger offshore turbineshave been developed due to their greater rated capacity and where a windfarm has a large number of wind turbines.

Therefore, a more efficient yet cost effective wind farm is desirablewhich solves these problems directed to wind turbine foundations,particularly in offshore structures, but not limited to this, and whichmakes wind energy industry projects economically more cost effective.

SUMMARY

A wind farm having a combination of technical features is hereindisclosed. The technical features include at least two wind turbines,each wind turbine including a foundation provided with a modular jacket,the modular jacket comprising a number of substructures connectable toeach other, wherein at least one substructure of one foundation isdifferent in height (h) from at least one substructure of the otherfoundation in order to adapt the wind turbines of the wind farm to asite having differences in depth (ΔH) where the wind turbines of thewind farm are to be installed.

Also disclosed is a method of installing such a wind farm. The wind farmcomprises at least two wind turbines to be installed in a site surface,each of which including a foundation provided with a modular jacketincluding at least an upper substructure, an intermediate substructure,and a lower substructure, at least the intermediate substructure in onefoundation being different in height (h) from at least the intermediatesubstructure in the other foundation in order to adapt the differentwind turbines to a site having differences in depth (ΔH) where the windturbines are installed, the method comprising, for each wind turbine:

-   -   providing the lower substructure;    -   fitting piles into the site surface;    -   attaching the piles to the lower substructure;    -   attaching the intermediate substructure to the lower        substructure; and    -   attaching the upper substructure to the intermediate        substructure.

As stated above, a wind farm as used herein comprises two or more windturbines installed in the same location, such as offshore, onshore, etc.for producing electric power.

The wind turbines in the wind farm comprise a tower and a nacelle. Thenacelle is rotatably mounted on the tower. A rotor hub provided withrotor blades is rotatably mounted on the rotor hub. The nacelle housesan electrical generator that is connected to the rotor blades. Powercontrol and mechanical equipment is also received into the nacelle. Therotor blades are caused to spin as they are struck by the wind. Therotational energy of the rotor blades is converted into electricalenergy within the generator. The resulting electrical energy istransformed by a transformer and fed into the electricity grid.

Wind turbine towers are in turn supported by a foundation structure. Thefoundation advantageously comprises a modular jacket. The modularjackets in the present wind farm are formed of a number ofsubstructures. The substructures of the modular jacket are connectableto each other.

In the present wind farm at least one of the substructures of themodular jacket of one wind turbine is different in height from at leastone substructure of another modular jacket. Such height difference inthe different wind turbines of the wind farm is such that thefoundation, i.e. the modular jacket, can be well adapted to a site withvariable depths. The term depth as used herein when referring tooffshore applications, i.e. sea depth, is intended to designate thedistance or height from the sea level to the sea bed, in the same windfarm site where wind turbines are installed.

As stated above, the modular jacket of the wind turbines in the presentwind farm are formed of a number of substructures. In one example, thesesubstructures may be at least an upper substructure, an intermediatesubstructure, and a lower substructure. These substructures areconnectable to each other. The jacket may include grouted connectionsfor connecting the substructures to each other.

The upper substructure may have at least one inclined portion while theintermediate substructure may be substantially vertical. Thesubstantially vertical configuration of the intermediate substructure isadvantageous since it provides a good resistance to the large bendingmoments induced by the wind and wave loads. On the other hand, the lowersubstructure may comprise at least one inclined portion and may includea foot unit. This foot unit of the lower substructure may include anumber of pins. The pins may be adapted for receiving at least oneportion of the length of corresponding piles. The piles are adapted tobe inserted into a surface of the site, such as the sea bed in offshoreapplications. A grouting chamber may be defined between the pin and thepile for receiving grout in order to establish a grouted connection.

According to one important feature of the present wind farm, at leastthe intermediate substructure in one wind turbine foundation isdifferent in height from at least the intermediate substructure inanother wind turbine foundation. This allows different wind turbines ofthe wind farm to be easily adapted to a site where varying sea depthsare present, thus reducing overall costs associated with wind turbinefoundations in the wind farm. The remainder substructures in at leasttwo different wind turbine foundations may be at least similar in heightto each other.

In practice, the present wind farm is such that at least onesubstructure in a wind turbine foundation that is different in heightfrom at least one substructure in another wind turbine foundation.Different wind turbines in the wind farm can be adapted easily and withlower costs to a site where sea depth varies for example from about 20to 60 m.

Due to the modular nature of the jacket in the above disclosed windfarm, a number of specific substructures of jacket may be standardized.This makes foundations easier to manufacture in series resulting inlower manufacturing costs. This advantage is more important as thenumber of wind turbines in the wind farm increases. Complexity isreduced as the number of jacket substructures having different designsis greatly reduced, that is, fewer site-specific parts have to bemanufactured. Logistics of the whole wind farm is thus facilitated. Thepresent wind farm is particularly advantageous in arrangements includinga large number of wind turbines.

The method for installing the above described wind farm comprisesproviding the lower substructure; fitting piles into the site surfacesuch as the sea bed; attaching the piles to the lower substructure;attaching the intermediate substructure to the lower substructure; andattaching the upper substructure to the intermediate substructure.

In some advantageous embodiments, at least one of the attachments of theintermediate substructure to the lower substructure and the uppersubstructure to the intermediate substructure is a grouting attachment.

Additional objects, advantages and features of embodiments of thepresent wind farm will become apparent to those skilled in the art uponexamination of the description, or may be learned by practice thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure refers to particular embodiments of the presentwind farm shown by way of non-limiting examples in the appendeddrawings.

In said drawings:

FIG. 1 a diagrammatically shows a wind farm of the prior art;

FIGS. 1 b and 1 c are perspective and elevational views respectively ofthe jacket structure in the wind turbines of the prior art wind farmshown in FIG. 1 a;

FIG. 2 diagrammatically shows one example of the present wind farm; and

FIG. 3 is an exploded elevational view of one example of a modularjacket in which the upper substructure, the intermediate substructure,and the lower substructure have been depicted in an unassembled state.

DETAILED DESCRIPTION OF EMBODIMENTS

One example of a standard prior art wind farm 100 is shown in FIG. 1 ofthe drawings. One example of the present wind farm 500 is shown in FIGS.2-3 of the drawings. Throughout the description of all the views in thedrawings, like reference numerals refer to like parts.

The wind farm 100 of the prior art shown in FIG. 1 comprises three windturbines 101, 102, 103. The present wind farm 500 shown in FIG. 2comprises two wind turbines 501, 502. A different number of windturbines other than those depicted for the wind farms 100 and 500 arealso possible as long as they comprise two or more wind turbines.

The wind farms 100, 500 have their corresponding wind turbines 101, 102,103, 501, 502 each installed in a corresponding site 10. In thisspecific example, the site 10 of the wind farms 100, 500 is offshore. Inthe bottom of the site 10, that is, the sea bed 600, the wind turbines101, 102, 103, 501, 502 are partly fitted.

The wind turbines 101, 102, 103, 501, 502 in both wind farms 100, 500respectively comprise a tower 200 and a nacelle 210. The nacelle 210 isrotatably mounted on the tower 200. A rotor is rotatably mounted on thenacelle 210. The rotor conventionally comprises a hub having rotorblades 220.

The rotor blades 220 are caused to spin as they are struck by the windwhich rotational energy is converted into electrical energy within agenerator (not shown) placed within the nacelle 210. The electricalenergy is transformed by a transformer (not shown) and fed into theelectricity grid.

The tower 200 of wind turbines 101, 102, 103, 501, 502 in both windfarms 100, 500 are supported by a foundation. The foundation of the windturbines 101, 102, 103 in the wind farm 100 of the prior art shown inFIGS. 1 a, 1 b and 1 c comprises a standard jacket 300. The foundationof the wind turbines 501, 502 in the present wind farm 500 shown inFIGS. 2 and 3 comprises a modular jacket 300′. The jackets 300, 300′ areadapted to transfer loads from the wind turbine tower 200 to the bottomof the site 10. The jackets 300, 300′ of the wind farms 100, 500 aredesigned according to the conditions of the site 10.

One important site condition in the present example of offshoreapplications is sea depths H1, H2 . . . , and more specifically thedifference between sea depths ΔH=H1−H2. As shown in the figures, thewater depths H1, H2 . . . correspond to the different values of thedistance or height from the sea level 601 to the sea bed 600 in theparticular site 10 of the wind farm 100, 500.

The examples of the wind turbines 101, 102 and 103 in the wind farm 100of the prior art in FIG. 1 show different strategies used to adaptjacket structures to sites having different characteristics. This hasbeen illustrated merely as an example: in the same wind farm, only onestrategy is usually adopted.

In the configuration of the foundation in wind turbine 102 theinclination of the jacket is similar to that of the wind turbine 101while the size of the foot unit (distance between piles) is different.In contrast, in the configuration of the foundation in wind turbine 103the size of the foot unit (distance between piles) is not varied whilethe inclination of the jacket is different. Therefore, wind turbines 102and 103 show two different strategies to obtain a high level ofstandardization.

However, in the present wind farm 500 shown in FIGS. 2 and 3, thestrategy is quite different. Specifically, the foundation in the presentwind farm 500 comprises a modular jacket 300′. The modular jacket 300′is adapted to be pinned into the sea bed 600 by means of piles 346. Themodular jacket 300′ consists of a frame that is suitably formed of threemodules or substructures 310, 320, 330. The substructures 310, 320, 330are connectable to each other through suitable grouted connections.

Now referring to FIG. 3 of the drawings, the first module of the jacket300′ is the upper substructure or transition piece 310. This is intendedto support the wind turbine tower 200. The transition piece 310 furtherincludes a working platform 315. The working platform 315 is arrangedjust below the wind turbine tower 200 as shown in FIG. 3.

Continuing with the example shown in FIG. 3, the second module of thejacket 300′ is an intermediate substructure 320. The intermediatesubstructure 320 is formed of a number of substantially vertical mainconnecting members 325 and a number of oblique secondary connectingmembers 326. The substantially vertical configuration of theintermediate substructure 320 can provide good resistance to largebending moments induced by the wind and wave loads present at the site10 where the wind turbines 501, 502 are installed.

Again referring to FIG. 3 of the drawings, the third module of thejacket 300′ is a lower substructure 330. The lower substructure 330comprises one inclined portion 335 and a foot unit 340. The foot unit340 is advantageously used in the present embodiment as a template forpilling. Specifically, the foot unit 340 of the lower substructure 330includes four pins 345. The pins 345 are arranged spaced at a distance dapart from each other. The pins 345 are conveniently adapted forreceiving at least one portion of the length of corresponding piles 346.When installing the foundation, the piles 346 are inserted into the seabed 600 and into the pins 345. Between the pins 345 and the piles 346 agrouting chamber is defined (not shown) for receiving grout.

In the present wind farm 500 shown in FIGS. 2 and 3 of the drawings, theintermediate substructure 320 in the wind turbines 501, 502 aredifferent in height h from each other. Differences in height h betweenthe wind turbines 501, 502 of the wind farm 500 allows the modularjackets 300′ to be well adapted to the different sea depths H1, H2 . . .of the sea bed 600 at the site 10 where the wind turbines 501, 502 areinstalled.

Manufacturing only intermediate substructures 320 to account for windturbines 501, 502 with different heights h from each other is more costeffective than manufacturing different whole jacket structures toaccount for differences in wind turbine heights. This can be carried outfor example by inserting brace elements and adapting the tubularthicknesses and diameters of the connecting members 325, 326 of theintermediate substructures 320. Other elements such as the piles 346depend not only on differences in sea depths ΔH=H1−H2 and loads, but onthe soil type. Piles 346 are also site-specific like the intermediatesubstructures 320. Piles 346 may vary in height, while diameter may beconstant. This is not, however, a problem since manufacture of severaltypes of piles 346 is cost effective.

The remaining substructures, that is, the upper and lower substructures310, 330 of different wind turbines 501, 502 may be at least similar inheight to each other. In one example, the intermediate substructures 320in the wind turbines 501, 502 can be well adapted to sites 10 wheredifferences in the sea depth ΔH=H1−H2 range from about 20 to 60 m, suchas 40 m. For example, H1 may be of the order of 15 m and H2 may be ofthe order of 55 m.

The main inclined portion 335 of the lower substructure 330 issubstantially vertical in each wind turbine 501, 502 of the present windfarm 500 as stated above. This means the distance d between the pins 345is constant regardless of differences in the sea depth ΔH at the site10.

In contrast, the standard jackets 300 of the wind turbines 101, 102 inthe wind farm 100 of the prior art shown in FIGS. 1 a, 1 b, 1 c shouldbe manufactured quite differently as to height and inclination in orderto be adapted for the varying conditions of the site 10. As clearlyshown in FIG. 1 a of the drawings, the inclination of the connectingmembers 300 as between wind turbines 101, 103 varies according to thedifferences in the sea depth ΔH at the site 10. This has undesirableconsequences in higher manufacturing, installation and transportationcosts.

In the present modular configuration of the jacket 300 of the presentwind farm 500 the upper and lower substructures 310, 330 may be thusstandardized while adapting the intermediate substructure 320 in heighth to the differences in the sea depth ΔH at the site 10. The presentjacket structures 300 are easier to manufacture in series whichadvantage is more important as the number of wind turbines 501, 502 inthe wind farm 500 increases.

The wind farm (500) may be installed by first providing the lowersubstructure (330), then fitting piles (346) into the site surface (600)and subsequently attaching said piles (346) to the lower substructure(330). The intermediate substructure (320) is then attached to the lowersubstructure (330) and the upper substructure (310) is finally attachedto the intermediate substructure (320). It is preferred that saidattachments, i.e. that of the intermediate substructure (320) to thelower substructure (330) and the upper substructure (310) to theintermediate substructure (320), are grouting attachments.

Although only a number of particular embodiments and examples of thepresent wind farm have been disclosed herein, it will be understood bythose skilled in the art that other alternative embodiments and/or usesand obvious modifications and equivalents thereof are possible.

For example, the embodiment of present wind farm has been disclosed foroffshore. In this particular application, one important varying featureis the sea depth. In this case, the sea depth has been defined herein asthe distance from the sea level to the sea bed. For the purposes of thepresent wind farm, depth differences ΔH may range from about 20 to about60 m. However, the present wind farm may also be of the onshore type, inwhich case, the important varying feature is the height. In onshoreapplications, the height may be defined as the distance from the groundto the hub. Therefore, this disclosure covers all possible embodimentsof the present wind farm and combinations thereof. Thus, the scope ofthe present disclosure should not be limited by particular embodiments,but should be determined only by a fair reading of the claims thatfollow.

1. A wind farm comprising: at least two wind turbines, each wind turbineincluding a foundation provided with a modular jacket, the modularjacket comprising a number of substructures connectable to each other,wherein at least one substructure of one foundation is different inheight (h) from at least one substructure of the other foundation inorder to adapt the wind turbines of the wind farm to a site havingdifferences in depth (ΔH) where the wind turbines of the wind farm areto be installed.
 2. The wind farm (500) of claim 1, wherein the modularjacket comprises at least an upper substructure, an intermediatesubstructure, and a lower substructure, the substructures beingconnectable to each other, and wherein at least the intermediatesubstructure in the one wind turbine foundation is different in height(h) from at least the intermediate substructure in the other windturbine foundation in order to adapt the different wind turbines of thewind farm to the site having differences in depth (ΔH) where the windturbines of the wind farm are installed.
 3. The wind farm of claim 2,wherein the upper substructure and lower substructure of the onefoundation is at least similar in height (h) to the respective uppersubstructure and lower substructure of the other foundation.
 4. The windfarm of claim 2, wherein the lower substructure comprises a foot unitincluding a number of pins that are adapted for receiving at least oneportion of a length of corresponding piles suitable for being insertedinto a surface of the site.
 5. The wind farm of claim 4, wherein agrouting chamber is defined between the pins and the piles for receivinggrout in order to establish a grouted connection.
 6. The wind farm ofclaim 1, wherein the modular jacket includes grouted connections forconnecting the substructures to each other.
 7. The-wind farm of claim 1,wherein the at least one substructure of the one foundation that isdifferent in height (h) from the at least one substructure in the otherfoundation is such that the at least two wind turbines in the wind farmcan be adapted to the site where differences in depth (ΔH) range fromabout 20 to 60 m.
 8. The wind farm of claim 2, wherein the uppersubstructure of the modular jacket has at least one inclined portion. 9.The wind farm of claim 2, wherein the intermediate substructure of themodular jacket is substantially vertical.
 10. The wind farm of claim 2,wherein the lower substructure of the modular jacket has at least oneinclined portion.
 11. A method for installing a wind farm, the wind farmcomprising at least two wind turbines to be installed in a site surface,each of which including a foundation provided with a modular jacketincluding at least an upper substructure, an intermediate substructure,and a lower substructure, at least the intermediate substructure in onefoundation being different in height (h) from at least the intermediatesubstructure in the other foundation in order to adapt the differentwind turbines to a site having differences in depth (ΔH) where the windturbines are installed, the method comprising, for each wind turbine:providing the lower substructure; fitting piles into the site surface;attaching the piles to the lower substructure; attaching theintermediate substructure to the lower substructure; and attaching theupper substructure to the intermediate substructure.
 12. The method ofclaim 11, wherein at least one attachment of the intermediatesubstructure to the lower substructure and the upper substructure to theintermediate substructure is a grouting attachment.